Weed wisdom

ON THE GARDEN PATH by Carolyn Herriot

A weed is a wild herb springing 

where it is not wanted. 
– Concise Oxford Dictionary

Weed seeds arrive with birds, on the wind, on our shoes and clothing and on a pet’s fur. They are persistent, lying dormant until conditions are just right for germination. Digging the soil brings weed seeds up to the surface, which helps them germinate. Perennial weeds can spread quickly by division when each little piece roots into a new plant. These are two good reasons to practise no-dig gardening and regular mulching.

Tip: Hoe weeds before they set seed and multiply your problem.

A garden will always have weeds, but there’s a great deal to be learned from observing them. There’s always a good reason why weeds spring up in the first place. An infestation points to an imbalance in the soil, such as poor drainage, lack of aeration, low fertility or a mineral deficiency. Weeds often thrive in poor soils, which indicates that the soil is deficient in the essentials for healthy plant growth.

Many perennial weeds are deep rooted, penetrating into the sub-soil where they access trace elements and minerals. When they decompose, their leaves and stems enrich the soil with these valuable elements, which may not otherwise be available to shallow-rooted plants. It’s important to return weeds to the soil for this reason, either by composting them or turning them under to decay in the garden. Deep roots also penetrate to aerate soil, helping with drainage. Dandelions, which thrive on heavy clay soils, are great at this.

Weeds can be used as indicators of general problems and they can even correct imbalances and deficiencies Weeds disappear when these conditions are corrected and soil conditions favour the growth of other plants – hopefully, not other weeds. The solution to a weed infestation, therefore, is to improve soil fertility, not to zap the area with soil-destroying herbicides. As Ralph Waldo Emerson noted, a weed is a “…plant whose virtues have not yet been discovered.”

What weeds can tell us:

• Daisies, rich in calcium, thrive on lawns lacking in lime. When daisies decompose, they add calcium to correct this deficiency.

• Equisetum (horsetail) indicates an acid, clay soil in need of drainage. If the soil is drained and fertility increases, horsetail will disappear.

• Docks, sorrel and thistles indicate heavy, badly drained and acid soils.

• Dandelions indicate that the soil lacks essential minerals and elements.

• Clovers, medicks, vetches and wild peas (legumes) indicate a nitrogen deficiency and can correct this condition in the soil.

• Creeping buttercup thrives in heavy, poorly drained soils.

• Bindweed generally thrives in sandy soils.

• Stinging nettles prefer light, sandy soils. High in nitrogen, nettles stimulate the growth of plants nearby.

• Chickweed, groundsel, chicory and lambsquarters are shallow-rooted weeds that grow in fertile conditions. They indicate an improvement in fertility.

Comfrey and stinging nettles make high quality liquid fertilizers. By extracting minerals from the sub-soil and storing them in their leaves, nettles and comfrey become rich in nitrogen, potassium and calcium. Nettles are also high in iron. When nettle leaves are steeped in rainwater, the resulting concentrate can be used as a feed, releasing nutrients to plants.

Nature never leaves the ground uncovered. In winter, weeds give protection from rains and their roots penetrate to aid with drainage. They also provide a store of food for soil bacteria, which can then remain active to provide food for plants in spring. Where groundcovers remain and flourish in winter, the result is increased soil fertility.

Carolyn Herriot is author of A Year on the Garden Path: A 52-Week Organic Gardening Guide. She grows her certified organic “Seeds of Victoria” at The Garden Path Centre where she blogs The New Victory Garden online.

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